Heretofore, air impermeable compositions such as those utilized for inner liners in tires were made from butyl type rubbers. Such compositions, although having low permeability to air, were expensive. Natural rubber was often added to such butyl type compositions to provide higher tensile strength and high cured adhesion to a tire carcass compound. However, the air permeability was increased since the air permeability of natural rubber is higher than that of butyl type rubber compounds.
Various elastomer blends containing fillers therein such as carbon black have been mixed with each other with respect to investigating various chemical and physical properties. For example, an article "Carbon Black Distribution in Elastomer Blends" by Hess, Scott, and Callan, Rubber Chemistry and Technology, pages 371 through 383, Volume 40, 1967, discusses the degree of subdivision of different polymer systems and the distribution of reinforcing filler particles between the phases.
Elastomer Blends, Compatibility and Relative Response to Fillers by Callan, Hess and Scott, pages 815-837, Rubber Chemistry and Technology, 1971, relates to zone size variations among different polymer blends, compatibility of butadiene rubber and sytrene-butadiene rubber, filler distribution between separate polymer phases as influenced by fundamental polymer and filler characteristics and carbon black transfer.
The article, Effect of Heterogeneous Carbon Black Distribution on the Properties of Polymer Blends by Sicar, Lamond, and Pinter, pages 48-56, Rubber Chemistry and Technology, 1974, relates to comparisons of blends of varying compatibility, for example, styrene-bytadiene rubber and polybutadiene rubber, styrene-butadiene rubber and natural rubber, and polybutadiene rubber and chlorobutyl rubber. Further, the article Elastomer Blend Properties-Influence of Carbon Black Type and Location by Hess and Chirico, pages 301-326, Rubber Chemistry and Technology, Volume 50, 1977, relates to the study of various blends of different types of rubber and their performance as affected by carbon black.
Finally, the article Experimental Studies of the Relationship of Processing to the Crack Growth of Carbon-Black-Loaded SBR-Cis-Polybutadiene Compounds by Biing-lin Lee, Journal of Applied Polymer Science, Volume 27, pages 3379-3392 (1982), relates to multicomponent polymer systems which are blended together to achieve improved results.
However, none of these articles relate to or suggest the blending of any separate but similar rubber compounds of fillers to yield different and unexpected results such as improvement with regard to air impermeability.